An impact assessment showed that, after the six-month follow-up period, the experimental group had lower rates of relapse and recidivism. However, they were less likely to be admitted to treatment, and the effects on recidivism were short-lived. Over time, the rate of recidivism increased, but the rate of drug abuse decreased [1].
The study had an experimental design, examining the differences among the three groups in relation to relapse and recidivism at two points in time: immediately after drug testing (six months) and at the end of the study period (18 months). The experimental group received frequent, randomized drug testing with immediate feedback and immediate sanctions. The first control group received frequent, randomized drug testing with delayed feedback and delayed sanctions. The second control group received non-randomized drug tests with delayed results and delayed sanctions. In general, the results were mixed [1].